The crosslinking of silicon-based polymers with organic peroxides is known. In particular, siloxanes have been cured by heating in the presence of an appropriate peroxide. However, little has been reported about the peroxide-crosslinking of polysilazanes.
In 1984, Kazakova et al. found that organooligocyclosilazanes, prepared by the catalytic condensation of a variety of cyclosilazanes, could be crosslinked by heating with 0.5-2.5 wt % of the silyl peroxide (MeSiOO.sup.t BuO).sub.x. The peroxide cure was particularly effective for silazanes with vinyl groups--up to 63% of a methylvinyloligocyclosilazane could be crosslinked by heating to 220.degree. C. Several polysilazane precursor systems have used this chemistry to produce high char yield solids.
U.S. Pat. No. 3,700,712, R. L. OSTROZYNSKI, discloses a process for preparing a silicon peroxide compound by reacting a dimethylamino silicon compound with a hydroperoxide compound.
U.S. Pat. No. 3,843,703, R. L. OSTROZYNSKI, teaches a process for preparing a silicon peroxide compound, which is not a polysilazane, by reacting a silazane compound with more than one molar equivalent of a hydroperoxide compound per equivalent of nitrogen in the silazane.
U.S. Pat. No. 4,772,494, H. PORTE et al., teaches a method of spinning fibers and coating using an organopolysilazane composition that can be crosslinked by an energy input. The organopolysilazane composition comprises an organopolysilazane and a free radical generator in an amount effective to crosslink the organopolysilazane.
U.S. Pat. No. 4,722,988, H. PORTE et al., discloses an organopolysilazane composition that can be crosslinked by an energy input. The organopolysilazane composition comprises an organopolysilazane and a free radical generator in an amount effective to crosslink the organopolysilazane.
U.S. Pat. No. 5,021,533, J. M. SCHWARK, discloses crosslinkable poly(thio)ureasilazane compositions comprising a poly(thio)ureasilazane and a free radical generator in an amount effective to crosslink the poly(thio)ureasilazane.
In U.S. Pat. Nos. 4,772,494, 4,772,988 and 5,021,533, the organopolysilazane is not a self-thermosetting polymer. In these patents, the peroxide must be mixed into the polymer before it can be thermoset.
U.S. Pat. Nos. 3,700,712 and 3,843,703 both produce silyl peroxides ending with alkyl or aryl substituents on silicon peroxide groups. During the silyl peroxide synthesis, the amine groups are lost as free amine and no ammonium halide salt is formed.